Dual-acting hydraulic dampers, also known as shock absorbers, may be utilized to damp the external forces applied to a vehicle, like an automobile. Dual-acting dampers refer to dampers that are effective in damping both the compression and the rebound of the damper. Compression refers to the damper shortening or compressing. Rebound refers to the damper lengthening or rebounding.
Dual-acting hydraulic dampers used on vehicles typically include a hollow cylinder defining an internal chamber which is divided into a compression compartment and an expansion compartment by a piston. The piston is slidably positioned in the internal chamber. A closed end of the cylinder is connected to the unsprung mass of the vehicle via a mount, like an eyelet. The piston rod extends through a seal assembly mounted on the other end of the hollow cylinder for movement relative to the cylinder. The piston rod has its inner end connected to the piston for movement therewith and its projecting end terminates in another mount (or eyelet) connectable to the vehicle.
When the piston is moved within the hollow cylinder, valving within the cylinder and piston may permit fluid to flow between the compression and rebound compartments (depending on the direction). The flow of the hydraulic fluid between these two compartments is known as the compression bleed circuit and the rebound bleed circuit, respectively. The damping characteristics of such dual-acting hydraulic dampers are determined by the rate at which fluid is permitted to flow between the compression and rebound compartments through the compression bleed circuit and the rebound bleed circuit. These rates may control the speed at which the piston may move in the cylinder responsive to the external forces applied to the damper.
One problem with known dual-acting hydraulic dampers of this type is the different volumes of the rebound and compression compartments. This may cause the bleed circuits to be unequal. Because the piston rod has to be connected to the piston through the rebound chamber, the piston rod forces the volume of the rebound chamber to be significantly smaller than the volume of the compression chamber. This requires a large collection chamber to accommodate the extra hydraulic fluid pumped from the compression chamber. This large collection chamber requires extra space and materials.
Another problem with a dual-acting shock of this type is the limited adjustments that have been included. Those working in the art have long recognized the desirability of being able to change or adjust the rate of fluid flow so that the damping characteristics of a shock absorber of this type may be changed to accommodate the varying conditions applied to the vehicle. Adjustable damping shock absorbers have been proposed in the past and have included mechanisms for selectively changing the rate of fluid flow. These prior mechanisms share the disadvantages of requiring structurally complex individual components. The complexity is a result of the need to provide adjustment of the primary fluid flow path of the shock absorber, the inaccessibility of the location of the flow adjustment, and the need to provide for adjustment over a wide range of flows. This complexity results in relatively high fabrication and/or assembly costs.
Typically, a dual-acting hydraulic damper of this type may include one or two separate adjustments. For example, the damper may include: an adjustment for high speed compression; two adjustments, one for high speed compression and one for high speed rebound; or two adjustments, one for high speed compression and one for low speed compression. However, no known dual-acting hydraulic damper has been provided with four independent damping adjustments, a first for high speed compression, a second for low speed compression, a third for high speed rebound, and a fourth for low speed rebound.
The instant invention is designed to address the above mentioned problems.